Over 1 million people with co-occurring substance abuse and mental health disorders (CODs) are booked into U.S. jails each year. Women with CODs may be especially vulnerable to entering the justice system, as indicated by evidence that twice as many women in jail have CODs as compared to men. Drug treatment court programs exist widely throughout the U.S., diverting substance abusing offenders into treatment instead of jail. However, they do not necessarily meet the treatment needs of offenders with CODs. Other types of diversion programs do exist that accommodate people with CODs and direct them to treatment for both disorders. One such program exists statewide in Connecticut. Existing evidence suggests that jail diversion programs reduce recidivism and increase engagement in treatment services among participants. It is unknown, however, if and how jail diversion works differently for men and women, given unique, gender-specific needs and risk factors. That women are diverted at a higher rate than men has long been the subject of speculation among diversion experts, and the rapid increase in incarceration among women appears to be related mainly to drug use and convictions. Gender may have important influences on how interventions like jail diversion work to engage participants in treatment services and reduce recidivism. Identifying significant gender differences in the effectiveness of jail diversion programs would provide important early information regarding if and how this intervention needs to be adapted to address the respective needs of men and women to improve their program outcomes. Under NIDA's B/START program PAR-12-251, Part 1 of the revised proposed project will be a longitudinal, cross-agency record study of 3,500 people with CODs, half of whom participated in a statewide jail diversion program in Connecticut during 2007-2009. The study will use quasi-experimental analyses to model gender differences among diversion participants and their non-diverted counterparts in clinical, demographic, and CJ characteristics; use of treatment and support services as part of the diversion program; use of crisis care (psychiatric hospitalizations and emergency department visits); and rates and types of recidivism after initiating diversion. Part 2 of the project will involve focus groups with jail diversion professionals to better understand the key gender-specific risk and protective factors for CJ involvement, diversion program selection and engagement, and outcomes. This study responds to B/START interest in co- morbid drug abuse and mental illness and innovative treatment approaches by learning about how men and women are selected into jail diversion programs, the treatment services they each use while in the program, and the related differential effects on their recovery and CJ involvement. The study will produce preliminary data to inform a larger research agenda to identify the constellation of risk factors for CJ involvement among men and women with CODs and adapt jail diversion programs to meet their respective unique treatment needs, thereby improving their chances for improved health and well-being and reduced recidivism.